Nazo no Kanojo X
Every girl is a mystery when you're a 16-year-old boy, but Mikoto Urabe is in another league. She carries scissors hidden in her panties. She sleeps on her desk every day. She seems to have no friends whatsoever. But none of that can compare to what happens when Tsubaki Akira decides on a whim to taste a drop of her drool while Urabe sleeps.
From that moment onward, things between Urabe and Akira are never the same, and the mysterious girl slowly becomes Akira's mysterious girlfriend. Along with their friends Ueno Kouhei and Oka Ayuko, Akira and Urabe try and navigate the minefield of high school first romance and all the strange things that happen along the way.